It is known that prostheses implanted inside the human body can be subject to infections.
When this occurs, the infected prosthesis must be removed from the implantation site and, before implanting another prosthesis, it is necessary for the infection to be eradicated.
During such a step, spacer devices are normally used in order to keep the shape of the bone seat or of the joint seat in which the new prosthesis will be implanted substantially unchanged.
Such a procedure is known as “two-step treatment” for the removal of an infected prosthesis and the implantation of a new prosthesis.
Such spacer devices do, however, have some limitations in terms of the amount or type of pharmaceutical or medical substance that can be released or, furthermore, in terms of the possibility of ensuring substantially uniform release of such a substance. Furthermore, it should be observed that in the case in which a spacer device has only the outer surface porous, the amount of pharmaceutical or medical substance that can be impregnated in the spacer device is limited by the depth and by the extension of the porous surface itself. In this case, the spacer device could not be able to ensure the release of the pharmaceutical or medical substance for a period equal to that necessary to completely heal the infected site.
Finally, there are spacer devices that are made from a biocompatible material that has pores for the entire volume occupied by the device itself.
Such spacers are, however, usually preloaded with a given antibiotic or with a given medical or pharmaceutical substance and, therefore, the surgeon does not have the freedom to choose which drug to use, hence being unable to adapt the drug itself to the patient's real needs.
Therefore, there is a need to have a spacer device that ensures uniform and constant release of the pharmaceutical or medical substance present through the entire outer surface of the spacer device itself, even for prolonged periods.
There are also preformed spacer devices that are produced by casting antibiotic-loaded bone cement in a mold until it sets, removing the mold and extracting the set spacer device, which is then processed or finished according to requirements.
Alternatively, the surgeon can make a spacer himself during the operation, using molds, usually made from silicone of suitable geometry, which are filled with antibiotic-loaded bone cement, to which a further antibiotic different from the first is optionally added. Once polymerization has taken place, the surgeon extracts the spacer from the silicone mold, facilitated by the flexible nature of this material, and then proceeds with the implanting, also in this case possibly finishing the spacer if necessary.
Therefore, there is a need for the surgeon to be able to choose the pharmaceutical or medical substance to be applied to the spacer device itself, so as to meet the specific needs of the patient.
At the same time, this possibility is associated with the need to have, in any case, a temporary and/or disposable spacer device of predetermined and correct shape and size, without the risk of the surgeon, having to make the spacer device directly in situ, being able to obtain a shape that is irregular or incompatible with the actual anatomical requirements of the patient, or in any case to be finished and processed before implanting.